pack-bitmap.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "tag.h"
   4 #include "diff.h"
   5 #include "revision.h"
   6 #include "progress.h"
   7 #include "list-objects.h"
   8 #include "pack.h"
   9 #include "pack-bitmap.h"
  10 #include "pack-revindex.h"
  11 #include "pack-objects.h"
  12
  13 /*
  14  * An entry on the bitmap index, representing the bitmap for a given
  15  * commit.
  16  */
  17 struct stored_bitmap {
  18         unsigned char sha1[20];
  19         struct ewah_bitmap *root;
  20         struct stored_bitmap *xor;
  21         int flags;
  22 };
  23
  24 /*
  25  * The currently active bitmap index. By design, repositories only have
  26  * a single bitmap index available (the index for the biggest packfile in
  27  * the repository), since bitmap indexes need full closure.
  28  *
  29  * If there is more than one bitmap index available (e.g. because of alternates),
  30  * the active bitmap index is the largest one.
  31  */
  32 static struct bitmap_index {
  33         /* Packfile to which this bitmap index belongs to */
  34         struct packed_git *pack;
  35
  36         /* reverse index for the packfile */
  37         struct pack_revindex *reverse_index;
  38
  39         /*
  40          * Mark the first `reuse_objects` in the packfile as reused:
  41          * they will be sent as-is without using them for repacking
  42          * calculations
  43          */
  44         uint32_t reuse_objects;
  45
  46         /* mmapped buffer of the whole bitmap index */
  47         unsigned char *map;
  48         size_t map_size; /* size of the mmaped buffer */
  49         size_t map_pos; /* current position when loading the index */
  50
  51         /*
  52          * Type indexes.
  53          *
  54          * Each bitmap marks which objects in the packfile  are of the given
  55          * type. This provides type information when yielding the objects from
  56          * the packfile during a walk, which allows for better delta bases.
  57          */
  58         struct ewah_bitmap *commits;
  59         struct ewah_bitmap *trees;
  60         struct ewah_bitmap *blobs;
  61         struct ewah_bitmap *tags;
  62
  63         /* Map from SHA1 -> `stored_bitmap` for all the bitmapped commits */
  64         khash_sha1 *bitmaps;
  65
  66         /* Number of bitmapped commits */
  67         uint32_t entry_count;
  68
  69         /* Name-hash cache (or NULL if not present). */
  70         uint32_t *hashes;
  71
  72         /*
  73          * Extended index.
  74          *
  75          * When trying to perform bitmap operations with objects that are not
  76          * packed in `pack`, these objects are added to this "fake index" and
  77          * are assumed to appear at the end of the packfile for all operations
  78          */
  79         struct eindex {
  80                 struct object **objects;
  81                 uint32_t *hashes;
  82                 uint32_t count, alloc;
  83                 khash_sha1_pos *positions;
  84         } ext_index;
  85
  86         /* Bitmap result of the last performed walk */
  87         struct bitmap *result;
  88
  89         /* Version of the bitmap index */
  90         unsigned int version;
  91
  92         unsigned loaded : 1;
  93
  94 } bitmap_git;
  95
  96 static struct ewah_bitmap *lookup_stored_bitmap(struct stored_bitmap *st)
  97 {
  98         struct ewah_bitmap *parent;
  99         struct ewah_bitmap *composed;
 100
 101         if (st->xor == NULL)
 102                 return st->root;
 103
 104         composed = ewah_pool_new();
 105         parent = lookup_stored_bitmap(st->xor);
 106         ewah_xor(st->root, parent, composed);
 107
 108         ewah_pool_free(st->root);
 109         st->root = composed;
 110         st->xor = NULL;
 111
 112         return composed;
 113 }
 114
 115 /*
 116  * Read a bitmap from the current read position on the mmaped
 117  * index, and increase the read position accordingly
 118  */
 119 static struct ewah_bitmap *read_bitmap_1(struct bitmap_index *index)
 120 {
 121         struct ewah_bitmap *b = ewah_pool_new();
 122
 123         int bitmap_size = ewah_read_mmap(b,
 124                 index->map + index->map_pos,
 125                 index->map_size - index->map_pos);
 126
 127         if (bitmap_size < 0) {
 128                 error("Failed to load bitmap index (corrupted?)");
 129                 ewah_pool_free(b);
 130                 return NULL;
 131         }
 132
 133         index->map_pos += bitmap_size;
 134         return b;
 135 }
 136
 137 static int load_bitmap_header(struct bitmap_index *index)
 138 {
 139         struct bitmap_disk_header *header = (void *)index->map;
 140
 141         if (index->map_size < sizeof(*header) + 20)
 142                 return error("Corrupted bitmap index (missing header data)");
 143
 144         if (memcmp(header->magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE)) != 0)
 145                 return error("Corrupted bitmap index file (wrong header)");
 146
 147         index->version = ntohs(header->version);
 148         if (index->version != 1)
 149                 return error("Unsupported version for bitmap index file (%d)", index->version);
 150
 151         /* Parse known bitmap format options */
 152         {
 153                 uint32_t flags = ntohs(header->options);
 154
 155                 if ((flags & BITMAP_OPT_FULL_DAG) == 0)
 156                         return error("Unsupported options for bitmap index file "
 157                                 "(Git requires BITMAP_OPT_FULL_DAG)");
 158
 159                 if (flags & BITMAP_OPT_HASH_CACHE) {
 160                         unsigned char *end = index->map + index->map_size - 20;
 161                         index->hashes = ((uint32_t *)end) - index->pack->num_objects;
 162                 }
 163         }
 164
 165         index->entry_count = ntohl(header->entry_count);
 166         index->map_pos += sizeof(*header);
 167         return 0;
 168 }
 169
 170 static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
 171                                           struct ewah_bitmap *root,
 172                                           const unsigned char *sha1,
 173                                           struct stored_bitmap *xor_with,
 174                                           int flags)
 175 {
 176         struct stored_bitmap *stored;
 177         khiter_t hash_pos;
 178         int ret;
 179
 180         stored = xmalloc(sizeof(struct stored_bitmap));
 181         stored->root = root;
 182         stored->xor = xor_with;
 183         stored->flags = flags;
 184         hashcpy(stored->sha1, sha1);
 185
 186         hash_pos = kh_put_sha1(index->bitmaps, stored->sha1, &ret);
 187
 188         /* a 0 return code means the insertion succeeded with no changes,
 189          * because the SHA1 already existed on the map. this is bad, there
 190          * shouldn't be duplicated commits in the index */
 191         if (ret == 0) {
 192                 error("Duplicate entry in bitmap index: %s", sha1_to_hex(sha1));
 193                 return NULL;
 194         }
 195
 196         kh_value(index->bitmaps, hash_pos) = stored;
 197         return stored;
 198 }
 199
 200 static inline uint32_t read_be32(const unsigned char *buffer, size_t *pos)
 201 {
 202         uint32_t result = get_be32(buffer + *pos);
 203         (*pos) += sizeof(result);
 204         return result;
 205 }
 206
 207 static inline uint8_t read_u8(const unsigned char *buffer, size_t *pos)
 208 {
 209         return buffer[(*pos)++];
 210 }
 211
 212 static int load_bitmap_entries_v1(struct bitmap_index *index)
 213 {
 214         static const size_t MAX_XOR_OFFSET = 160;
 215
 216         uint32_t i;
 217         struct stored_bitmap **recent_bitmaps;
 218
 219         recent_bitmaps = xcalloc(MAX_XOR_OFFSET, sizeof(struct stored_bitmap));
 220
 221         for (i = 0; i < index->entry_count; ++i) {
 222                 int xor_offset, flags;
 223                 struct ewah_bitmap *bitmap = NULL;
 224                 struct stored_bitmap *xor_bitmap = NULL;
 225                 uint32_t commit_idx_pos;
 226                 const unsigned char *sha1;
 227
 228                 commit_idx_pos = read_be32(index->map, &index->map_pos);
 229                 xor_offset = read_u8(index->map, &index->map_pos);
 230                 flags = read_u8(index->map, &index->map_pos);
 231
 232                 sha1 = nth_packed_object_sha1(index->pack, commit_idx_pos);
 233
 234                 bitmap = read_bitmap_1(index);
 235                 if (!bitmap)
 236                         return -1;
 237
 238                 if (xor_offset > MAX_XOR_OFFSET || xor_offset > i)
 239                         return error("Corrupted bitmap pack index");
 240
 241                 if (xor_offset > 0) {
 242                         xor_bitmap = recent_bitmaps[(i - xor_offset) % MAX_XOR_OFFSET];
 243
 244                         if (xor_bitmap == NULL)
 245                                 return error("Invalid XOR offset in bitmap pack index");
 246                 }
 247
 248                 recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
 249                         index, bitmap, sha1, xor_bitmap, flags);
 250         }
 251
 252         return 0;
 253 }
 254
 255 static char *pack_bitmap_filename(struct packed_git *p)
 256 {
 257         char *idx_name;
 258         int len;
 259
 260         len = strlen(p->pack_name) - strlen(".pack");
 261         idx_name = xmalloc(len + strlen(".bitmap") + 1);
 262
 263         memcpy(idx_name, p->pack_name, len);
 264         memcpy(idx_name + len, ".bitmap", strlen(".bitmap") + 1);
 265
 266         return idx_name;
 267 }
 268
 269 static int open_pack_bitmap_1(struct packed_git *packfile)
 270 {
 271         int fd;
 272         struct stat st;
 273         char *idx_name;
 274
 275         if (open_pack_index(packfile))
 276                 return -1;
 277
 278         idx_name = pack_bitmap_filename(packfile);
 279         fd = git_open_noatime(idx_name);
 280         free(idx_name);
 281
 282         if (fd < 0)
 283                 return -1;
 284
 285         if (fstat(fd, &st)) {
 286                 close(fd);
 287                 return -1;
 288         }
 289
 290         if (bitmap_git.pack) {
 291                 warning("ignoring extra bitmap file: %s", packfile->pack_name);
 292                 close(fd);
 293                 return -1;
 294         }
 295
 296         bitmap_git.pack = packfile;
 297         bitmap_git.map_size = xsize_t(st.st_size);
 298         bitmap_git.map = xmmap(NULL, bitmap_git.map_size, PROT_READ, MAP_PRIVATE, fd, 0);
 299         bitmap_git.map_pos = 0;
 300         close(fd);
 301
 302         if (load_bitmap_header(&bitmap_git) < 0) {
 303                 munmap(bitmap_git.map, bitmap_git.map_size);
 304                 bitmap_git.map = NULL;
 305                 bitmap_git.map_size = 0;
 306                 return -1;
 307         }
 308
 309         return 0;
 310 }
 311
 312 static int load_pack_bitmap(void)
 313 {
 314         assert(bitmap_git.map && !bitmap_git.loaded);
 315
 316         bitmap_git.bitmaps = kh_init_sha1();
 317         bitmap_git.ext_index.positions = kh_init_sha1_pos();
 318         bitmap_git.reverse_index = revindex_for_pack(bitmap_git.pack);
 319
 320         if (!(bitmap_git.commits = read_bitmap_1(&bitmap_git)) ||
 321                 !(bitmap_git.trees = read_bitmap_1(&bitmap_git)) ||
 322                 !(bitmap_git.blobs = read_bitmap_1(&bitmap_git)) ||
 323                 !(bitmap_git.tags = read_bitmap_1(&bitmap_git)))
 324                 goto failed;
 325
 326         if (load_bitmap_entries_v1(&bitmap_git) < 0)
 327                 goto failed;
 328
 329         bitmap_git.loaded = 1;
 330         return 0;
 331
 332 failed:
 333         munmap(bitmap_git.map, bitmap_git.map_size);
 334         bitmap_git.map = NULL;
 335         bitmap_git.map_size = 0;
 336         return -1;
 337 }
 338
 339 static int open_pack_bitmap(void)
 340 {
 341         struct packed_git *p;
 342         int ret = -1;
 343
 344         assert(!bitmap_git.map && !bitmap_git.loaded);
 345
 346         prepare_packed_git();
 347         for (p = packed_git; p; p = p->next) {
 348                 if (open_pack_bitmap_1(p) == 0)
 349                         ret = 0;
 350         }
 351
 352         return ret;
 353 }
 354
 355 int prepare_bitmap_git(void)
 356 {
 357         if (bitmap_git.loaded)
 358                 return 0;
 359
 360         if (!open_pack_bitmap())
 361                 return load_pack_bitmap();
 362
 363         return -1;
 364 }
 365
 366 struct include_data {
 367         struct bitmap *base;
 368         struct bitmap *seen;
 369 };
 370
 371 static inline int bitmap_position_extended(const unsigned char *sha1)
 372 {
 373         khash_sha1_pos *positions = bitmap_git.ext_index.positions;
 374         khiter_t pos = kh_get_sha1_pos(positions, sha1);
 375
 376         if (pos < kh_end(positions)) {
 377                 int bitmap_pos = kh_value(positions, pos);
 378                 return bitmap_pos + bitmap_git.pack->num_objects;
 379         }
 380
 381         return -1;
 382 }
 383
 384 static inline int bitmap_position_packfile(const unsigned char *sha1)
 385 {
 386         off_t offset = find_pack_entry_one(sha1, bitmap_git.pack);
 387         if (!offset)
 388                 return -1;
 389
 390         return find_revindex_position(bitmap_git.reverse_index, offset);
 391 }
 392
 393 static int bitmap_position(const unsigned char *sha1)
 394 {
 395         int pos = bitmap_position_packfile(sha1);
 396         return (pos >= 0) ? pos : bitmap_position_extended(sha1);
 397 }
 398
 399 static int ext_index_add_object(struct object *object, const char *name)
 400 {
 401         struct eindex *eindex = &bitmap_git.ext_index;
 402
 403         khiter_t hash_pos;
 404         int hash_ret;
 405         int bitmap_pos;
 406
 407         hash_pos = kh_put_sha1_pos(eindex->positions, object->sha1, &hash_ret);
 408         if (hash_ret > 0) {
 409                 if (eindex->count >= eindex->alloc) {
 410                         eindex->alloc = (eindex->alloc + 16) * 3 / 2;
 411                         REALLOC_ARRAY(eindex->objects, eindex->alloc);
 412                         REALLOC_ARRAY(eindex->hashes, eindex->alloc);
 413                 }
 414
 415                 bitmap_pos = eindex->count;
 416                 eindex->objects[eindex->count] = object;
 417                 eindex->hashes[eindex->count] = pack_name_hash(name);
 418                 kh_value(eindex->positions, hash_pos) = bitmap_pos;
 419                 eindex->count++;
 420         } else {
 421                 bitmap_pos = kh_value(eindex->positions, hash_pos);
 422         }
 423
 424         return bitmap_pos + bitmap_git.pack->num_objects;
 425 }
 426
 427 static void show_object(struct object *object, const struct name_path *path,
 428                         const char *last, void *data)
 429 {
 430         struct bitmap *base = data;
 431         int bitmap_pos;
 432
 433         bitmap_pos = bitmap_position(object->sha1);
 434
 435         if (bitmap_pos < 0) {
 436                 char *name = path_name(path, last);
 437                 bitmap_pos = ext_index_add_object(object, name);
 438                 free(name);
 439         }
 440
 441         bitmap_set(base, bitmap_pos);
 442 }
 443
 444 static void show_commit(struct commit *commit, void *data)
 445 {
 446 }
 447
 448 static int add_to_include_set(struct include_data *data,
 449                               const unsigned char *sha1,
 450                               int bitmap_pos)
 451 {
 452         khiter_t hash_pos;
 453
 454         if (data->seen && bitmap_get(data->seen, bitmap_pos))
 455                 return 0;
 456
 457         if (bitmap_get(data->base, bitmap_pos))
 458                 return 0;
 459
 460         hash_pos = kh_get_sha1(bitmap_git.bitmaps, sha1);
 461         if (hash_pos < kh_end(bitmap_git.bitmaps)) {
 462                 struct stored_bitmap *st = kh_value(bitmap_git.bitmaps, hash_pos);
 463                 bitmap_or_ewah(data->base, lookup_stored_bitmap(st));
 464                 return 0;
 465         }
 466
 467         bitmap_set(data->base, bitmap_pos);
 468         return 1;
 469 }
 470
 471 static int should_include(struct commit *commit, void *_data)
 472 {
 473         struct include_data *data = _data;
 474         int bitmap_pos;
 475
 476         bitmap_pos = bitmap_position(commit->object.sha1);
 477         if (bitmap_pos < 0)
 478                 bitmap_pos = ext_index_add_object((struct object *)commit, NULL);
 479
 480         if (!add_to_include_set(data, commit->object.sha1, bitmap_pos)) {
 481                 struct commit_list *parent = commit->parents;
 482
 483                 while (parent) {
 484                         parent->item->object.flags |= SEEN;
 485                         parent = parent->next;
 486                 }
 487
 488                 return 0;
 489         }
 490
 491         return 1;
 492 }
 493
 494 static struct bitmap *find_objects(struct rev_info *revs,
 495                                    struct object_list *roots,
 496                                    struct bitmap *seen)
 497 {
 498         struct bitmap *base = NULL;
 499         int needs_walk = 0;
 500
 501         struct object_list *not_mapped = NULL;
 502
 503         /*
 504          * Go through all the roots for the walk. The ones that have bitmaps
 505          * on the bitmap index will be `or`ed together to form an initial
 506          * global reachability analysis.
 507          *
 508          * The ones without bitmaps in the index will be stored in the
 509          * `not_mapped_list` for further processing.
 510          */
 511         while (roots) {
 512                 struct object *object = roots->item;
 513                 roots = roots->next;
 514
 515                 if (object->type == OBJ_COMMIT) {
 516                         khiter_t pos = kh_get_sha1(bitmap_git.bitmaps, object->sha1);
 517
 518                         if (pos < kh_end(bitmap_git.bitmaps)) {
 519                                 struct stored_bitmap *st = kh_value(bitmap_git.bitmaps, pos);
 520                                 struct ewah_bitmap *or_with = lookup_stored_bitmap(st);
 521
 522                                 if (base == NULL)
 523                                         base = ewah_to_bitmap(or_with);
 524                                 else
 525                                         bitmap_or_ewah(base, or_with);
 526
 527                                 object->flags |= SEEN;
 528                                 continue;
 529                         }
 530                 }
 531
 532                 object_list_insert(object, &not_mapped);
 533         }
 534
 535         /*
 536          * Best case scenario: We found bitmaps for all the roots,
 537          * so the resulting `or` bitmap has the full reachability analysis
 538          */
 539         if (not_mapped == NULL)
 540                 return base;
 541
 542         roots = not_mapped;
 543
 544         /*
 545          * Let's iterate through all the roots that don't have bitmaps to
 546          * check if we can determine them to be reachable from the existing
 547          * global bitmap.
 548          *
 549          * If we cannot find them in the existing global bitmap, we'll need
 550          * to push them to an actual walk and run it until we can confirm
 551          * they are reachable
 552          */
 553         while (roots) {
 554                 struct object *object = roots->item;
 555                 int pos;
 556
 557                 roots = roots->next;
 558                 pos = bitmap_position(object->sha1);
 559
 560                 if (pos < 0 || base == NULL || !bitmap_get(base, pos)) {
 561                         object->flags &= ~UNINTERESTING;
 562                         add_pending_object(revs, object, "");
 563                         needs_walk = 1;
 564                 } else {
 565                         object->flags |= SEEN;
 566                 }
 567         }
 568
 569         if (needs_walk) {
 570                 struct include_data incdata;
 571
 572                 if (base == NULL)
 573                         base = bitmap_new();
 574
 575                 incdata.base = base;
 576                 incdata.seen = seen;
 577
 578                 revs->include_check = should_include;
 579                 revs->include_check_data = &incdata;
 580
 581                 if (prepare_revision_walk(revs))
 582                         die("revision walk setup failed");
 583
 584                 traverse_commit_list(revs, show_commit, show_object, base);
 585         }
 586
 587         return base;
 588 }
 589
 590 static void show_extended_objects(struct bitmap *objects,
 591                                   show_reachable_fn show_reach)
 592 {
 593         struct eindex *eindex = &bitmap_git.ext_index;
 594         uint32_t i;
 595
 596         for (i = 0; i < eindex->count; ++i) {
 597                 struct object *obj;
 598
 599                 if (!bitmap_get(objects, bitmap_git.pack->num_objects + i))
 600                         continue;
 601
 602                 obj = eindex->objects[i];
 603                 show_reach(obj->sha1, obj->type, 0, eindex->hashes[i], NULL, 0);
 604         }
 605 }
 606
 607 static void show_objects_for_type(
 608         struct bitmap *objects,
 609         struct ewah_bitmap *type_filter,
 610         enum object_type object_type,
 611         show_reachable_fn show_reach)
 612 {
 613         size_t pos = 0, i = 0;
 614         uint32_t offset;
 615
 616         struct ewah_iterator it;
 617         eword_t filter;
 618
 619         if (bitmap_git.reuse_objects == bitmap_git.pack->num_objects)
 620                 return;
 621
 622         ewah_iterator_init(&it, type_filter);
 623
 624         while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
 625                 eword_t word = objects->words[i] & filter;
 626
 627                 for (offset = 0; offset < BITS_IN_WORD; ++offset) {
 628                         const unsigned char *sha1;
 629                         struct revindex_entry *entry;
 630                         uint32_t hash = 0;
 631
 632                         if ((word >> offset) == 0)
 633                                 break;
 634
 635                         offset += ewah_bit_ctz64(word >> offset);
 636
 637                         if (pos + offset < bitmap_git.reuse_objects)
 638                                 continue;
 639
 640                         entry = &bitmap_git.reverse_index->revindex[pos + offset];
 641                         sha1 = nth_packed_object_sha1(bitmap_git.pack, entry->nr);
 642
 643                         if (bitmap_git.hashes)
 644                                 hash = ntohl(bitmap_git.hashes[entry->nr]);
 645
 646                         show_reach(sha1, object_type, 0, hash, bitmap_git.pack, entry->offset);
 647                 }
 648
 649                 pos += BITS_IN_WORD;
 650                 i++;
 651         }
 652 }
 653
 654 static int in_bitmapped_pack(struct object_list *roots)
 655 {
 656         while (roots) {
 657                 struct object *object = roots->item;
 658                 roots = roots->next;
 659
 660                 if (find_pack_entry_one(object->sha1, bitmap_git.pack) > 0)
 661                         return 1;
 662         }
 663
 664         return 0;
 665 }
 666
 667 int prepare_bitmap_walk(struct rev_info *revs)
 668 {
 669         unsigned int i;
 670         unsigned int pending_nr = revs->pending.nr;
 671         struct object_array_entry *pending_e = revs->pending.objects;
 672
 673         struct object_list *wants = NULL;
 674         struct object_list *haves = NULL;
 675
 676         struct bitmap *wants_bitmap = NULL;
 677         struct bitmap *haves_bitmap = NULL;
 678
 679         if (!bitmap_git.loaded) {
 680                 /* try to open a bitmapped pack, but don't parse it yet
 681                  * because we may not need to use it */
 682                 if (open_pack_bitmap() < 0)
 683                         return -1;
 684         }
 685
 686         for (i = 0; i < pending_nr; ++i) {
 687                 struct object *object = pending_e[i].item;
 688
 689                 if (object->type == OBJ_NONE)
 690                         parse_object_or_die(object->sha1, NULL);
 691
 692                 while (object->type == OBJ_TAG) {
 693                         struct tag *tag = (struct tag *) object;
 694
 695                         if (object->flags & UNINTERESTING)
 696                                 object_list_insert(object, &haves);
 697                         else
 698                                 object_list_insert(object, &wants);
 699
 700                         if (!tag->tagged)
 701                                 die("bad tag");
 702                         object = parse_object_or_die(tag->tagged->sha1, NULL);
 703                 }
 704
 705                 if (object->flags & UNINTERESTING)
 706                         object_list_insert(object, &haves);
 707                 else
 708                         object_list_insert(object, &wants);
 709         }
 710
 711         /*
 712          * if we have a HAVES list, but none of those haves is contained
 713          * in the packfile that has a bitmap, we don't have anything to
 714          * optimize here
 715          */
 716         if (haves && !in_bitmapped_pack(haves))
 717                 return -1;
 718
 719         /* if we don't want anything, we're done here */
 720         if (!wants)
 721                 return -1;
 722
 723         /*
 724          * now we're going to use bitmaps, so load the actual bitmap entries
 725          * from disk. this is the point of no return; after this the rev_list
 726          * becomes invalidated and we must perform the revwalk through bitmaps
 727          */
 728         if (!bitmap_git.loaded && load_pack_bitmap() < 0)
 729                 return -1;
 730
 731         revs->pending.nr = 0;
 732         revs->pending.alloc = 0;
 733         revs->pending.objects = NULL;
 734
 735         if (haves) {
 736                 revs->ignore_missing_links = 1;
 737                 haves_bitmap = find_objects(revs, haves, NULL);
 738                 reset_revision_walk();
 739                 revs->ignore_missing_links = 0;
 740
 741                 if (haves_bitmap == NULL)
 742                         die("BUG: failed to perform bitmap walk");
 743         }
 744
 745         wants_bitmap = find_objects(revs, wants, haves_bitmap);
 746
 747         if (!wants_bitmap)
 748                 die("BUG: failed to perform bitmap walk");
 749
 750         if (haves_bitmap)
 751                 bitmap_and_not(wants_bitmap, haves_bitmap);
 752
 753         bitmap_git.result = wants_bitmap;
 754
 755         bitmap_free(haves_bitmap);
 756         return 0;
 757 }
 758
 759 int reuse_partial_packfile_from_bitmap(struct packed_git **packfile,
 760                                        uint32_t *entries,
 761                                        off_t *up_to)
 762 {
 763         /*
 764          * Reuse the packfile content if we need more than
 765          * 90% of its objects
 766          */
 767         static const double REUSE_PERCENT = 0.9;
 768
 769         struct bitmap *result = bitmap_git.result;
 770         uint32_t reuse_threshold;
 771         uint32_t i, reuse_objects = 0;
 772
 773         assert(result);
 774
 775         for (i = 0; i < result->word_alloc; ++i) {
 776                 if (result->words[i] != (eword_t)~0) {
 777                         reuse_objects += ewah_bit_ctz64(~result->words[i]);
 778                         break;
 779                 }
 780
 781                 reuse_objects += BITS_IN_WORD;
 782         }
 783
 784 #ifdef GIT_BITMAP_DEBUG
 785         {
 786                 const unsigned char *sha1;
 787                 struct revindex_entry *entry;
 788
 789                 entry = &bitmap_git.reverse_index->revindex[reuse_objects];
 790                 sha1 = nth_packed_object_sha1(bitmap_git.pack, entry->nr);
 791
 792                 fprintf(stderr, "Failed to reuse at %d (%016llx)\n",
 793                         reuse_objects, result->words[i]);
 794                 fprintf(stderr, " %s\n", sha1_to_hex(sha1));
 795         }
 796 #endif
 797
 798         if (!reuse_objects)
 799                 return -1;
 800
 801         if (reuse_objects >= bitmap_git.pack->num_objects) {
 802                 bitmap_git.reuse_objects = *entries = bitmap_git.pack->num_objects;
 803                 *up_to = -1; /* reuse the full pack */
 804                 *packfile = bitmap_git.pack;
 805                 return 0;
 806         }
 807
 808         reuse_threshold = bitmap_popcount(bitmap_git.result) * REUSE_PERCENT;
 809
 810         if (reuse_objects < reuse_threshold)
 811                 return -1;
 812
 813         bitmap_git.reuse_objects = *entries = reuse_objects;
 814         *up_to = bitmap_git.reverse_index->revindex[reuse_objects].offset;
 815         *packfile = bitmap_git.pack;
 816
 817         return 0;
 818 }
 819
 820 void traverse_bitmap_commit_list(show_reachable_fn show_reachable)
 821 {
 822         assert(bitmap_git.result);
 823
 824         show_objects_for_type(bitmap_git.result, bitmap_git.commits,
 825                 OBJ_COMMIT, show_reachable);
 826         show_objects_for_type(bitmap_git.result, bitmap_git.trees,
 827                 OBJ_TREE, show_reachable);
 828         show_objects_for_type(bitmap_git.result, bitmap_git.blobs,
 829                 OBJ_BLOB, show_reachable);
 830         show_objects_for_type(bitmap_git.result, bitmap_git.tags,
 831                 OBJ_TAG, show_reachable);
 832
 833         show_extended_objects(bitmap_git.result, show_reachable);
 834
 835         bitmap_free(bitmap_git.result);
 836         bitmap_git.result = NULL;
 837 }
 838
 839 static uint32_t count_object_type(struct bitmap *objects,
 840                                   enum object_type type)
 841 {
 842         struct eindex *eindex = &bitmap_git.ext_index;
 843
 844         uint32_t i = 0, count = 0;
 845         struct ewah_iterator it;
 846         eword_t filter;
 847
 848         switch (type) {
 849         case OBJ_COMMIT:
 850                 ewah_iterator_init(&it, bitmap_git.commits);
 851                 break;
 852
 853         case OBJ_TREE:
 854                 ewah_iterator_init(&it, bitmap_git.trees);
 855                 break;
 856
 857         case OBJ_BLOB:
 858                 ewah_iterator_init(&it, bitmap_git.blobs);
 859                 break;
 860
 861         case OBJ_TAG:
 862                 ewah_iterator_init(&it, bitmap_git.tags);
 863                 break;
 864
 865         default:
 866                 return 0;
 867         }
 868
 869         while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
 870                 eword_t word = objects->words[i++] & filter;
 871                 count += ewah_bit_popcount64(word);
 872         }
 873
 874         for (i = 0; i < eindex->count; ++i) {
 875                 if (eindex->objects[i]->type == type &&
 876                         bitmap_get(objects, bitmap_git.pack->num_objects + i))
 877                         count++;
 878         }
 879
 880         return count;
 881 }
 882
 883 void count_bitmap_commit_list(uint32_t *commits, uint32_t *trees,
 884                               uint32_t *blobs, uint32_t *tags)
 885 {
 886         assert(bitmap_git.result);
 887
 888         if (commits)
 889                 *commits = count_object_type(bitmap_git.result, OBJ_COMMIT);
 890
 891         if (trees)
 892                 *trees = count_object_type(bitmap_git.result, OBJ_TREE);
 893
 894         if (blobs)
 895                 *blobs = count_object_type(bitmap_git.result, OBJ_BLOB);
 896
 897         if (tags)
 898                 *tags = count_object_type(bitmap_git.result, OBJ_TAG);
 899 }
 900
 901 struct bitmap_test_data {
 902         struct bitmap *base;
 903         struct progress *prg;
 904         size_t seen;
 905 };
 906
 907 static void test_show_object(struct object *object,
 908                              const struct name_path *path,
 909                              const char *last, void *data)
 910 {
 911         struct bitmap_test_data *tdata = data;
 912         int bitmap_pos;
 913
 914         bitmap_pos = bitmap_position(object->sha1);
 915         if (bitmap_pos < 0)
 916                 die("Object not in bitmap: %s\n", sha1_to_hex(object->sha1));
 917
 918         bitmap_set(tdata->base, bitmap_pos);
 919         display_progress(tdata->prg, ++tdata->seen);
 920 }
 921
 922 static void test_show_commit(struct commit *commit, void *data)
 923 {
 924         struct bitmap_test_data *tdata = data;
 925         int bitmap_pos;
 926
 927         bitmap_pos = bitmap_position(commit->object.sha1);
 928         if (bitmap_pos < 0)
 929                 die("Object not in bitmap: %s\n", sha1_to_hex(commit->object.sha1));
 930
 931         bitmap_set(tdata->base, bitmap_pos);
 932         display_progress(tdata->prg, ++tdata->seen);
 933 }
 934
 935 void test_bitmap_walk(struct rev_info *revs)
 936 {
 937         struct object *root;
 938         struct bitmap *result = NULL;
 939         khiter_t pos;
 940         size_t result_popcnt;
 941         struct bitmap_test_data tdata;
 942
 943         if (prepare_bitmap_git())
 944                 die("failed to load bitmap indexes");
 945
 946         if (revs->pending.nr != 1)
 947                 die("you must specify exactly one commit to test");
 948
 949         fprintf(stderr, "Bitmap v%d test (%d entries loaded)\n",
 950                 bitmap_git.version, bitmap_git.entry_count);
 951
 952         root = revs->pending.objects[0].item;
 953         pos = kh_get_sha1(bitmap_git.bitmaps, root->sha1);
 954
 955         if (pos < kh_end(bitmap_git.bitmaps)) {
 956                 struct stored_bitmap *st = kh_value(bitmap_git.bitmaps, pos);
 957                 struct ewah_bitmap *bm = lookup_stored_bitmap(st);
 958
 959                 fprintf(stderr, "Found bitmap for %s. %d bits / %08x checksum\n",
 960                         sha1_to_hex(root->sha1), (int)bm->bit_size, ewah_checksum(bm));
 961
 962                 result = ewah_to_bitmap(bm);
 963         }
 964
 965         if (result == NULL)
 966                 die("Commit %s doesn't have an indexed bitmap", sha1_to_hex(root->sha1));
 967
 968         revs->tag_objects = 1;
 969         revs->tree_objects = 1;
 970         revs->blob_objects = 1;
 971
 972         result_popcnt = bitmap_popcount(result);
 973
 974         if (prepare_revision_walk(revs))
 975                 die("revision walk setup failed");
 976
 977         tdata.base = bitmap_new();
 978         tdata.prg = start_progress("Verifying bitmap entries", result_popcnt);
 979         tdata.seen = 0;
 980
 981         traverse_commit_list(revs, &test_show_commit, &test_show_object, &tdata);
 982
 983         stop_progress(&tdata.prg);
 984
 985         if (bitmap_equals(result, tdata.base))
 986                 fprintf(stderr, "OK!\n");
 987         else
 988                 fprintf(stderr, "Mismatch!\n");
 989 }
 990
 991 static int rebuild_bitmap(uint32_t *reposition,
 992                           struct ewah_bitmap *source,
 993                           struct bitmap *dest)
 994 {
 995         uint32_t pos = 0;
 996         struct ewah_iterator it;
 997         eword_t word;
 998
 999         ewah_iterator_init(&it, source);
1000
1001         while (ewah_iterator_next(&word, &it)) {
1002                 uint32_t offset, bit_pos;
1003
1004                 for (offset = 0; offset < BITS_IN_WORD; ++offset) {
1005                         if ((word >> offset) == 0)
1006                                 break;
1007
1008                         offset += ewah_bit_ctz64(word >> offset);
1009
1010                         bit_pos = reposition[pos + offset];
1011                         if (bit_pos > 0)
1012                                 bitmap_set(dest, bit_pos - 1);
1013                         else /* can't reuse, we don't have the object */
1014                                 return -1;
1015                 }
1016
1017                 pos += BITS_IN_WORD;
1018         }
1019         return 0;
1020 }
1021
1022 int rebuild_existing_bitmaps(struct packing_data *mapping,
1023                              khash_sha1 *reused_bitmaps,
1024                              int show_progress)
1025 {
1026         uint32_t i, num_objects;
1027         uint32_t *reposition;
1028         struct bitmap *rebuild;
1029         struct stored_bitmap *stored;
1030         struct progress *progress = NULL;
1031
1032         khiter_t hash_pos;
1033         int hash_ret;
1034
1035         if (prepare_bitmap_git() < 0)
1036                 return -1;
1037
1038         num_objects = bitmap_git.pack->num_objects;
1039         reposition = xcalloc(num_objects, sizeof(uint32_t));
1040
1041         for (i = 0; i < num_objects; ++i) {
1042                 const unsigned char *sha1;
1043                 struct revindex_entry *entry;
1044                 struct object_entry *oe;
1045
1046                 entry = &bitmap_git.reverse_index->revindex[i];
1047                 sha1 = nth_packed_object_sha1(bitmap_git.pack, entry->nr);
1048                 oe = packlist_find(mapping, sha1, NULL);
1049
1050                 if (oe)
1051                         reposition[i] = oe->in_pack_pos + 1;
1052         }
1053
1054         rebuild = bitmap_new();
1055         i = 0;
1056
1057         if (show_progress)
1058                 progress = start_progress("Reusing bitmaps", 0);
1059
1060         kh_foreach_value(bitmap_git.bitmaps, stored, {
1061                 if (stored->flags & BITMAP_FLAG_REUSE) {
1062                         if (!rebuild_bitmap(reposition,
1063                                             lookup_stored_bitmap(stored),
1064                                             rebuild)) {
1065                                 hash_pos = kh_put_sha1(reused_bitmaps,
1066                                                        stored->sha1,
1067                                                        &hash_ret);
1068                                 kh_value(reused_bitmaps, hash_pos) =
1069                                         bitmap_to_ewah(rebuild);
1070                         }
1071                         bitmap_reset(rebuild);
1072                         display_progress(progress, ++i);
1073                 }
1074         });
1075
1076         stop_progress(&progress);
1077
1078         free(reposition);
1079         bitmap_free(rebuild);
1080         return 0;
1081 }